AP® Physics 1 & 2

Four Particle Entropy

There are four particles of a substance distributed between two chambers of container that makes up an isolated system. The particles are in constant motion.

What is the probability of having all the particles on the left side of the container and how does this relate to entropy?

A

There is a 33% probability of finding all the particles on the left because they can all a be on the left, all on the right or split. This is entropy because entropy is the probability of a certain state of a substance.

B

There is a 6.25% probability of finding all the particles on the left because this is one of 16 possible microstates. This shows a low entropy because low probability is a highly ordered system.

C

There is a 50% probability of finding all the particles on the left because each particle is either on the right or on the left. This middle value for probability means that the entropy is the same as the probability that just one particle that could be either right or left.

D

The probability of finding all the particles on the left is not related to entropy because change in entropy is the heat energy transferred divided by average temperature.